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Genotypic characterization of bacterial strains obtained from leaf cheese using real-time PCR
Objective: To genotypically characterize bacterial strains isolated from queso de hoja (peeling cheese/soft white cheese wrapped in leaves) samples from the Hoya del río Suárez region, Colombia, using Real-Time PCR (qPCR) for the detection of specific virulence genes. Methods: A total of 58 bacterial strains (15 Salmonella sp. strains, 15 E. coli, 8 S. aureus, and 20 Listeria sp.), previously isolated from queso de hoja samples from the Hoya del río Suárez region, Colombia, were analyzed. Genomic DNA extraction was performed, and genotypic characterization was conducted using qPCR with primers for the eaeA, nucA, hlyA, and invA genes, respectively. Results: The standardization of the methodology was successful, achieving high efficiency and linearity. Regarding amplification in the samples, it proved to be highly effective: 73.3% of E. coli strains were positive for the eaeA gene, 100% of S. aureus strains for nucA, and 100% of Listeria sp. strains for hlyA. The specific modifications observed in the melting curve could suggest the existence of possible allelic variants in these strains. However, the absence of invA gene amplification in the 15 Salmonella sp. strains indicates the need for a future exhaustive molecular evaluation of these isolates. Conclusion: The successful standardization and genotypic characterization of the strains using qPCR was achieved, validating the methodology for the detection of virulence factors in bacterial isolates from queso de hoja.
